becomes (ActiveRecord::Persistence)

Neat, hadn't seen ActiveRecord #becomes before: Useful for STI + form_for with record identification.

Returns an instance of the specified klass with the attributes of the current record. This is mostly useful in relation to single-table inheritance structures where you want a subclass to appear as the superclass. This can be used along with record identification in Action Pack to allow, say, Client < Company to do something like render :partial => @client.becomes (Company ) to render that instance using the companies/company partial instead of clients/client. Note: The new instance will share a link to the same attributes as the original class. So any change to the attributes in either instance will affect the other.

Full article: http://apidock.com/rails/ActiveRecord/Persistence/becomes